An Improved structure for reducing parasitic capacitances in planar transformers for LLC resonant converters

Abstract

This study investigates the design of a planar transformer for a 48V/3A electric motorcycle charger utilizing an LLC resonant converter. While planar transformers with PCB windings offer advantages such as compact size and high power density, they are hindered by high parasitic capacitances, including intra- and inter-winding types, which degrade voltage regulation, soft-switching efficiency, and cause issues with electromagnetic interference (EMI). Existing strategies, such as shielding layers, split-turn windings, and zero common-mode current (ZCC) layouts, effectively reduce specific parasitic capacitances but fail to address both intra- and inter-winding capacitances simultaneously. To overcome these limitations, this study proposes an improved winding layout that comprehensively minimizes parasitic capacitances.